Centrifugal fan

ABSTRACT

A CASING FOR A CENTRIFUGAL FAN COMPRISING A HOLLOW BOX STRUCTURE HAVING SQUARE CORNERS, ONE END WALL HAVING AN EXHAUST OPENING AT ONE CORNER AND AN ANGULARLY DISPOSED SHIELDING PLATE AT THE OTHER CORNER. THE FAN WHEEL AXIS IS OFFSET FROM THE CENTER OF THE BOX TOWARD SAID SHIELDING PLATE. THE CASING IS PREFERABLY FORMED BY FOUR UNIFORMSIZED BOX-SHAPED ELEMENTS WHICH ARE ABUTTED AND JOINED AS SHOWN IN FIG. 1.

Feb. 9, 1971 KARL-ERIK FERMER 3,561,996

- CENTRIFUGAL FAN Filed Jan. 31, 1969 2 Sheets-Sheet 1 FIGI.

INVENTORZ KAR L ERI K FERME'R ATTYS.

1971 KARL-ERIK FERMER 3,561,906

CENTRIFUGAL FAN Filed Jan. 31, 1969 I 2 Sheets-Sheet 2 FIG. 2.

. INVENTOR'. B KARL-ERIK FERMER ATTYS,

United States Patent 3,561,906 CENTRIFUGAL FAN Karl-Erik Fermr,Jonkoping, Sweden, assignor to Aktiebolaget Svenska Flaktfabriken,Stockholm, Sweden Filed Jan. 31, 1969, Ser. No. 795,585 Claims priority,application Sweden, Jan. 31, 1968, 1 323/68 Int. Cl. F0 4d 29/40, 17/08US. Cl. 415-206 2 Claims ABSTRACT OF THE DISCLOSURE The presentinvention relates to a new and simple design of a centrifugal fanconsisting of a casing provided with inand outlets and a centrifugal fanwheel rotatably journalled in same.

The manufacture of centrifugal fans of conventional design, i.e. with aspiral-shaped casing, includes the following working moments:

(1) Contour cutting of the casing sides by means of a template.

(2) Forming the casing backplate to a curving radius varying in acertain manner.

(3) Joining the casing sides and backplate along a curved line.

These working moments depend on templates and special tools, and theyhave proved to be very time-consuming and represent a great lot of thetotal manufacturing cost. The invention is based on the discovery thatthe spiral-shaped fan casing without any worth mentioning deteriorationof the efficiency of the fan can be substituted by' a casing of a moresimple geometrical form, which has the result that the manufacturingcost can be considerably reduced. The new and characterizing feature forthe invention is that the casing is provided with two end walls, ofwhich one or both is equipped with said inlet and four intermediateplane walls, which walls are located mainly at such a distance from thecentre of the wheel that the walls form tangents to an imaginary backplate of conventional spiral shape, and that the wall being located atthe smallest distance from the centre of the wheel is provided with theabove-mentioned outlet located close to the corner line at the one ofthe plane walls touching each other, which is located at the greatestdistance from the centre of the wheel.

A suitable embodiment of the invention is characterized in that betweenthe plane wall located next to the centre of the wheel and thesubsequent plane wall is arranged a plate shielding the corner.

In order to further reduce the manufacturing cost and to simplify themounting especially of bigger fans the casing can be provided with twosquared or rectangular wall elements and four, preferably betweenthemselves uniform and box-shaped elements of same size each consistingof a bottom, two opposite rectangular side walls and an intermediate endwall, which box-shaped elements are arranged in a closed circuit inorder to enclose together a space with a squared or rectangularcross-section and with the end wall of each box-shaped element locatedin the same plane as the bottom in the abutting box-shaped 3,561,906Patented Feb. 9, 1971 "ice element and with the side walls of thebox-shaped elements connected to the above-mentioned squared orrectangular wall elements, of which at least one is provided with aninlet opening.

The invention will now be closer described with reference to theenclosed drawing showing an exemplifying embodiment of the invention.

FIG. 1 is a perspective view of a centrifugal fan embodying the presentinvention; and

FIG. 2 is a sectional view through the fan shown in FIG. 1.

In the drawing 1 designates a fan casing provided with an inlet 2 and anoutlet 3. 4 designates a fan wheel of centrifugal type, the shaft ofwhich 5 is rotatably journalled in two bearing houses 6 supported bystiffening means 7 fastened to the casing. The casing :1 is according tothe invention provided with two end walls 8 and 8 and four intermediateplane walls 10, 11, 12 and 13. The last-mentioned plane walls arelocated at such a distance from the centre of the wheel that they formtangents to an imaginary back plate 14 of conventional spiral shape.Between the walls 10 and 11 is in the case shown arranged a plate 15shielding the intermediate corner.

As shown in FIG. 1, the casing 1 is formed by four box-shaped peripheralelements designated 21, 22, 23, and 24, each element comprising a bottomwall a, and end wall b and side walls 0. The peripheral elements 21, 22,23 and 24 are arranged in closed circuit order so that the bottom 21-aand the end 22-h form the wall 11, the bottom 22-a. and the end 23-bform the wall 12, the bottom 23a and the end 24-b form the wall 13, andthe bottom 24-a and the end 21-b form the wall 10. The sides 0 form themarginal portions of the walls 8 and a filler element 25 having theinlet 2 is mounted to form the central part of the front wall 8, and asimilar filler element is provided to form the central part of the rearwall 8.

What I claim is:

1. In a centrifugal fan consisting of a casing and a centrifugal fanwheel rotatably journaled in said casing, said casing comprising twosides having square corners, at least one of said sides having an inletopening to the center of said fan wheel, four plane walls intermediatesaid sides around the boundary thereof to form a hollow box with squarecorners, said fan being journaled on an axis offset frorn'fthe center ofsaid sides towards a corner of said hollow box formed between a firstand a second of said plane walls so that all four of said Walls formtangents to an imaginary back plate of conventional spiral shape, saidfirst wall having an outlet opening therein adjacent to the cornerformed between said first wall and a fourth of said walls, and anoblique guiding surface in said first corner extending from said firstplane wall to said second plane wall, tangential to said imaginaryspiralshaped back plate, said four plane walls and said guide plateproviding an open casing directly confronting the fan wheel withoutinterposition of a back plate therebetween, the improvement wherein saidcasing comprises four boxlike peripheral elements interconnected in aclosed circuit, each element having a bottom, two opposite side portionsand an end, the bottom of each element being coplanar with the end of anadjacent element to provide said four plane walls, the respective sideportions of all elements being coplanar to form the outer marginal areaof said casing sides, and including filler elements positioned withinthe marginal area formed by said boxshaped elements to form the centralparts of said casing sides, at least one of said filler elements havingsaid inlet opening therein.

2. A centrifugal fan according to claim 1 wherein said 3,174,682 3/ 1965Wilfert et a1. 230133 box-like peripheral elements are of the same sizeand 3,312,389 4/1967 Matsui "230-127 said filler elements are square.3,286,914 11/1966 Bauerstock 230-133 References Cited 5 FOREIGN UNITEDSTATES PATENTS 741,975 12/1955 Great Britain 230128 2,482,519 9/1949SchWarz 230128 HENRY F. RADUAZO, Primary Examiner 2,557,201 6/1951 Punt230-433 2,659,294 11/1953 Hersperger 415-204 US. Cl. X.R.

2,854,188 9/1958 Shornphe 230-133 10 415204

